One of the main figures behind the Belfast Agreement has accused powerful USA politician Nancy Pelosi of using the deal to "blackmail" the United Kingdom over Brexit.
Following her stark warning on the terms of a US-UK trade deal, US House of Representatives speaker Nancy Pelosi will on Tuesday begin a two-day visit to Dublin as part of a Brexit-related mission to Europe.
She will be accompanied by a delegation of Democrat and Republican congressmen and women.
"The Good Friday accords ended 700 years..."
The high-ranking group of United States politicians will meet Irish prime minister Leo Varadkar on Tuesday afternoon, while Pelosi will speak to Irish parliament and meet the Irish president on Wednesday. "Frictionless movement was part of a strategy of "normalisation" of relations between Protestant and Catholic communities within Northern Ireland and across the border", the Institute for Government said, with the government calling it "the most tangible symbol of the Peace Process".
"I thought one of the biggest opportunities was for the US and the European Union to join together - the biggest market in the world, the two combined - and use that leverage in negotiations with the Chinese", Pelosi told an audience at the London School of Economics.
"It is an ideal; it is a value".
"It was a model and other people have used it as a model and we don't want that model to be something that can be bargained away in another agreement".
The future of the Northern Ireland border will be a particular focus, with Pelosi seeking to express "America's commitment to a peaceful and prosperous future" for all those who live in the two countries.
Media captionWho is Nancy Pelosi? "It is a value", she told an audience that included Irish Foreign Minister Simon Coveney.
On Wednesday she will meet Irish government and opposition politicians before addressing both houses of the Oireachtas (Irish parliament).
Ms Pelosi and the delegation are also due to meet Irish President Michael D Higgins at his official residence, Áras an Uachtaráin, in Dublin's Phoenix Park.
President Donald Trump, a supporter of Brexit, has said he is prepared to enter a "large scale" trade agreement with the British.
In London, she claimed the United States missed an opportunity to gain economic leverage over China when it opted to put tariffs on the European Union rather than join forces with it.